Patent GB-844286-A (GB)
Title: Process for the manufacture of pigmented particles of high-melting polyesters
IPC: D01F1/04
Filed: 1957-02-01
Abstract: High-melting spinnable polyesters (especially polyethylene terephthalate) are pigmented by applying to the surface of particles thereof a pigment dispersion which contains as a binder a film-forming polyester dissolved in a volatile solvent, and thereafter evaporating the solvent.  The pigment may be cadmium sulphide, iron oxide, chromous oxide, ultramarine, a colbalt pigment, carbon black, titanium dioxide, a metal phthalocyanine or a vat dye stuff e.g. of the anthraquinonoid or aminoanthraquinone type.  The film-forming polyester may be a polyester of (a) an aromatic dicarboxylic acid (e.g. iso- or terephthalic (with a glycol either or both of which components may contain substituents (e.g. alkyl, halogen or alkoxy groups) (b) a copolyester of an aromatic discarboxylic acid, an aliphatic dicarboxylic acid and a glycol (c) a copolyester of terephthalic acid, isophthalic acid and a glycol (e.g. ethylene-, 1, 3-propylene- or 1, 4-butylene glycol) (d) a polyester into which has been condensed minor quantities of amide-forming groups (e.g. diamines, amino alcohols or lactams).  The solvent may be methylene chloride, ethylene chloride, tetrachloroethane, or chlorobenzene alone or in admixture with ispropylalcohol nbutyl alcohol or glycol monoethyl ether.  To facilitate wetting of the pigment by the solvent, the pigment dispersion may contain a surface-active quarternary ammonium compound or a non-ionic surface-active agent containing a hydroxyethyl group which has been esterified with thionyl chloride or etherified with benzyl chloride. To increase the adhesive power of the pigment film to the surface of the polyester chips, the pigment dispersion may contain a swelling agent, e.g. chlorobenzene, tetrachloroethane, anisole, phenoxy ethanol, phenol or orthochlorophenol.  To obtain a better wetting effect the pigment may be given a prior treatment to render it more lipophilic.  The mixture of pigment and polyester which may contain a small quantity of solvent or swelling agent or the whole of the pigment dispersion may be mechanically homogenized.  The polyester particles are treated by heating them to 60 DEG -80 DEG C. in a mixing drum, slowly introducing the pigment dispersion whilst revolving the drum and allowing the solvent to evaporate.  When most of the solvent has been evaporated, a non-solvent (e.g. benzine, benzene or water) may be sprayed on to the coated polyester chips to accelerate soldification of the polyesterfilm and prevent it sticking to the walls of the mixing vessel.  The chips are then dried under reduced pressure at 140-180 DEG C.  In examples, polyethylene terephthalate chips are treated with a pigment dispersion containing (1) cadmium sulphide, a copolyester of terephthanic acid, isophthalic acid and ethylene glycol and methylene chloride, (2) a vat dyestuff formula;  <FORM:0844286/IV(a)/1> a copolymer of terephthalic acid, isophthalic acid, isosebacic acid and ethylene glycol, and methylene chloride, (3) a vat dyestuff of formula.  <FORM:0844286/IV(a)/2> a copolyester of terephthalic acid, isophthalic acid and ethylene glycol and methylene chloride.